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| United States Patent |
5,178,702
|
|
Frerking, Jr.
, et al.
|
January 12, 1993
|
Pneumatic tire having a multilayered innerliner
Abstract
The present invention relates to a pneumatic rubber tire having an integral
innerliner characterized by a top layer and a rubber laminate having at
least three additional layers. At least two of the three layers are
barrier layers and comprise a sulfur cured rubber composition containing,
based on 100 parts by weight of rubber, 100 parts of an
acrylonitrile/diene copolymer rubber having an acrylonitrile content
ranging from about 30 to about 45 percent and from about 25 to about 150
parts by weight of a platy filler selected from the group consisting of
talc, clay, mica or mixtures thereof. The thickness of each
acrylonitrile/diene barrier layer ranges from about 25 microns to 380
microns. Between the two layers of acrylonitrile/diene copolymer is at
least one non-barrier layer of a sulfur cured rubber selected from the
group consisting of natural rubber, halogenated butyl rubber, butyl
rubber, cis-1,4-polyisoprene, styrene-butadiene rubber,
cis-1,4-polybutadiene, styrene/isoprene/butadiene rubber or mixtures
thereof. The laminate may contain from about 3 to 100 individual layers.
| Inventors:
|
Frerking, Jr.; Harlan W. (Alliance, OH);
Smith; Richard R. (Cuyahoga Falls, OH)
|
| Assignee:
|
The Goodyear Tire & Rubber Company (Akron, OH)
|
| Appl. No.:
|
680656 |
| Filed:
|
April 4, 1991 |
| Current U.S. Class: |
152/510; 152/DIG.16 |
| Intern'l Class: |
B60C 005/14 |
| Field of Search: |
152/510,511,504,505,506,DIG. 16
|
References Cited
U.S. Patent Documents
| 2489995 | Nov., 1949 | Young | 152/347.
|
| 2541550 | Feb., 1951 | Sarbach et al. | 154/139.
|
| 2575249 | Nov., 1951 | Connell et al. | 154/139.
|
| 2676636 | Apr., 1954 | Sarbach | 152/330.
|
| 3038515 | Jun., 1962 | Koch et al. | 152/510.
|
| 3903947 | Sep., 1975 | Emerson | 152/504.
|
| 4256158 | Mar., 1981 | Chautard et al. | 152/330.
|
| 4388261 | Jun., 1983 | Codispoti et al. | 152/505.
|
| 4549593 | Oct., 1985 | Yahagi et al.
| |
| 4857409 | Aug., 1989 | Hazelton et al. | 428/494.
|
| 5005625 | Apr., 1991 | Klemmensen et al. | 152/510.
|
| Foreign Patent Documents |
| 0337279 | Oct., 1989 | EP.
| |
| 2198138 | Jun., 1988 | GB.
| |
Other References
R. J. Eldred, Dimensional Control Swelling in Nitrile Elastomers by
Anisometric Fillers, Rubber World, vol. 188 (1983).
Eldred et al, Platy Filler Effects on Fracture Energies and Flex Fatigue of
Elastomers, ACS Rubber Divison Fall 1989 Meeting.
R. J. Eldred, Effect of Oriented Platy Filler on the Fracture Mechanism of
Elastomers, Rubber Chemistry and Technology, vol. 61, Sep.-Oct. 1988.
|
Primary Examiner: Knable; Geoffrey L.
Attorney, Agent or Firm: Hendricks; Bruce J.
Claims
What is claimed is:
1. A pneumatic rubber tire having an integral innerliner comprising a top
layer and a rubber laminate having at least 3 additional layers wherein
said top layer is closed to the carcass of the tire and is comprised of a
sulfur cured rubber consisting of natural rubber, styrene-butadiene rubber
blends thereof and
(a) at least 2 of said 3 layers are barrier layers each comprised of a
sulfur cured rubber composition containing, based on 100 parts by weight
of rubber,
100parts by weight of acrylonitrile/diene copolymer having an acrylonitrile
content ranging from about 30 to 45% and form about 25 to about 150 parts
by weight of a platy filler selected from the group consisting of talc,
clay, mica or mixtures thereof; and
(b) the thickness of each barrier layer containing 100 parts by weight of
acrylonitrile/diene copolymer ranges from about 25 microns to 380 microns;
and
(c) between the 2 barrier layers of sulfur cured rubber containing 100
parts of acrylonitrile/diene copolymer is at least one nonbarrier layer of
a sulfur cured rubber selected form the group consisting of natural
rubber, halogenated butyl rubber, cis-1,4-polybutadiene, styrene/butadiene
rubber, cis-1,4-polyisoprene, styrene/isoprene/butadiene rubber, butyl
rubber or mixtures thereof.
2. The pneumatic tire of claim 1 wherein said innerliner consists of 3 to
100 layers.
3. The pneumatic tire of claim 1 wherein the platy filler is talc.
4. The pneumatic tire of claim 1 wherein the thickness of each of the
barrier layers containing 100 parts by weight of acrylonitrile/diene
copolymer ranges from about 100 microns to about 320 microns.
5. The pneumatic tire of claim 1 wherein said acrylonitrile/diene copolymer
is an acrylonitrile/butadiene rubber.
6. The pneumatic tire of claim 6 wherein said acrylonitrile/butadiene
rubber has an acrylonitrile content ranging from about 32% to about 40%.
7. The pneumatic tire of claim 1 wherein said innerliner consists of from 5
to 12 layers.
8. The pneumatic tire of claim 1 wherein the thickness of said nonbarrier
layer ranges from about 25 microns to about 1143 microns.
9. The pneumatic tire of claim 1 wherein said integral innerliner as a
cured innerliner has a total thickness of from about 0.02 to about 0.35
centimeters.
10. The pneumatic tire of claim 1 wherein said nonbarrier layer of sulfur
cured rubber has a thickness ranging from about 100 to about 508 microns.
Description
BACKGROUND OF THE INVENTION
The inner surface of a pneumatic tire is typically comprised of an
elastomeric composition designed to prevent or retard the permeation of
air and moisture into the carcass from the tire's inner air chamber. It is
often referred to as an innerliner. Innerliners have also been used for
many years in tubeless pneumatic vehicle tires to retard or prevent the
escape of air used to inflate the tire, thereby maintaining tire pressure.
Rubbers, such as butyl and halobutyl rubber, which are relatively
impermeable to air are often used as a major proportion of the
innerliners.
The innerliner is normally prepared by conventional calendering or milling
techniques to form a strip of uncured compounded rubber of appropriate
width which is sometimes referred to as a gum strip. Typically, the gum
strip is the first element of the tire applied to a tire building drum,
over and around which the remainder of the tire is built. When the tire is
cured, the innerliner becomes an integral, co-cured, part of the tire.
Tire innerliners and their methods of preparation are well known to those
having skill in such art.
Halobutyl rubber is generally the most expensive rubber used in a tire.
Given the competitive tire market and the continued need to lower the cost
of manufacturing tires without sacrificing properties, there exists a need
to eliminate or substantially decrease the cost of innerliners which
perform such an important function in the performance of a tire.
Acrylonitrile/butadiene copolymers are commonly known for having excellent
air impermeability. Since acrylonitrile/butadiene copolymers are
conventionally more economical than halobutyl rubbers, one would hope that
such acrylonitrile/butadiene copolymers could be utilized as an
innerliner. Unfortunately, acrylonitrile/butadiene copolymers suffer from
unacceptable flexural properties at low temperatures. Since a rubber used
in an innerliner must be flexible and the service life of a pneumatic tire
commonly involves severe low temperatures, the use of an
acrylonitrile/butadiene copolymer as an innerliner would be expected to
meet with failure.
SUMMARY OF THE INVENTION
The present invention relates to a pneumatic tire having a multi-layered
innerliner. Use of a top layer and a minimum of a 3 layered laminate, at
least two barrier layers being made from an acrylonitrile/diene copolymer,
results in significantly reducing the costs of the innerliner while
maintaining the overall barrier and flexibility required for tire
innerliner applications.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a pneumatic rubber tire having an integral innerliner
comprising a top layer on rubber laminate having at least 3 layers wherein
(a) at least 2 of said three layers are barrier layers each comprised of a
sulfur cured rubber composition containing, based on 100 parts by weight
of rubber,
100 parts by weight of acrylonitrile/diene copolymer having an
acrylonitrile content ranging from about 30 to 45% and from about 25 to
about 150 parts by weight of a platy filler selected from the group
consisting of talc, clay, mica or mixtures thereof; and
(b) the thickness of each barrier layer containing 100 parts by weight of
acrylonitrile/diene copolymer ranges from about 25 microns to 380 microns:
and
(c) between the 2 barrier layers of sulfur cured rubber containing 100
parts of acrylonitrile/diene copolymer is at least one nonbarrier layer of
a sulfur cured rubber selected from the group consisting of natural
rubber, halogenated butyl rubber, styrene/butadiene rubber,
cis-1,4-polybutadiene, cis-1,4-polyisoprene, styrene/isoprene/butadiene
rubber, butyl rubber or mixtures thereof.
The innerliner of the present invention is characterized by having a top
layer and at least three layers of a sulfur cured rubber composition.
Whereas three layers is the minimum, it is contemplated that one may have
up to one-hundred layers since the major limitation is being able to
produce and ply up each individual layer having a sufficiently low
thickness offset by the total thickness of the innerliner. Preferably, the
innerliner of the present invention comprises a top layer and a rubber
laminate having from about 5 to about 12 layers of a sulfur cured rubber
composition. Surprisingly, increasing the number of layers in the laminate
(for a given thickness) decreases low temperature stiffness (measured by
ASTM-1053-85). Increasing the number of layers also decreases low strain
modulus at room temperature while increasing high strain modulus.
The rubber laminate which is used as an innerliner contains at least two
barrier layers of a sulfur cured rubber composition each layer containing,
based on 100 parts by weight of rubber (phr), 100 phr of
acrylonitrile/diene copolymer having an acrylonitrile content ranging from
about 30 to about 45 percent. The acrylonitrile/diene copolymers are
intended to include acrylonitrile/butadiene and acrylonitrile isoprene
copolymers. Preferably, the acrylonitrile/diene copolymer is an
acrylonitrile/butadiene copolymer. The preferred acrylonitrile/diene
copolymer has an acrylonitrile content ranging from about 32 to about 40
percent. With increasing levels of acrylonitrile, the air permeability of
the acrylonitrile/diene rubber layer will increase. Unfortunately, with
increasing levels of acrylonitrile content, there is a decrease in the
flexural properties at frigid temperatures, i.e., below -35.degree. C. The
Mooney viscosity of the acrylonitrile-diene copolymer is not considered to
be a limiting feature.
The acrylonitrile/diene copolymer compound may contain up to 150 phr of a
platy filler. Preferably, the acrylonitrile/diene copolymer compound
contains from about 20 to 150 phr of a platy filler. Representative of the
platy fillers which may be used include talc, clay or mica. Preferably,
talc is used. The amount of platy filler that is preferred will depend on
the acrylonitrile/diene copolymer that is selected. For example, when
using an acrylonitrile/diene copolymer having an acrylonitrile content of
from about 30 to 35 percent, one may prefer to use the upper range with
respect to the parts by weight of the platy filler. On the other hand,
when one is using an acrylonitrile/diene copolymer having an acrylonitrile
content above 40%, one may be able to use a lower amount of the platy
filler.
The thickness of each acrylonitrile/diene copolymer barrier layer in the
innerliner may vary depending on the number of layers in the laminate as
well as the total thickness desired of the innerliner. Generally speaking,
the thickness of each acrylonitrile/diene copolymer-containing barrier
layer ranges from about 25 microns (1 mil) to about 380 microns (15 mils).
Preferably, the thickness of each of these barrier layers range from about
100 microns (4 mils) to about 320 microns (12 mils).
Between the 2 barrier layers of sulfur cured rubber containing the 100
parts of acrylonitrile/diene copolymer is at least one layer (nonbarrier
layer) of a conventional rubber used in pneumatic tires. Representative of
such rubbers include natural rubber, halogenated butyl rubber, butyl
rubber, cis-1,4-polyisoprene, styrene-butadiene rubber,
cis-1,4-polybutadiene, styrene-isoprene-butadiene rubber or mixtures
thereof. Preferably, the layer is composed of natural rubber,
styrene-butadiene rubber or mixtures thereof.
The thickness of each non-barrier layer in the innerliner may vary
depending on the number of layers in the laminate as well as the total
thickness desired of the innerliner. Generally speaking, the thickness of
each non-barrier layer may range from about 25 microns (1 mil) to about
1143 microns (45 mils). Preferably, the thickness of each non-barrier
layer may range from about 100 microns (4 mils) to about 508 microns (20
mils).
While the innerliner may have various layers of different compounds, it is
preferred to have the top layer (layer closest to the carcass of the tire)
be a nonbarrier layer for compatibility reasons and especially if the
abutting carcass rubber is the same rubber as the top layer of the
innerliner.
The various rubber compositions which make up each layer of the innerliner,
including layers containing the acrylonitrile/diene rubber, may be
compounded with conventional rubber compounding ingredients. Conventional
ingredients commonly used in rubber vulcanizates are, for example, carbon
black, tackifier resins, processing aids, antioxidants, antiozonants,
stearic acid, activators, waxes, oils and peptizing agents. As known to
those skilled in the art, depending on the intended use of the sulfur
vulcanized rubber, certain additives mentioned above are commonly used in
conventional amounts. Typical additions of carbon black comprise from
about 10 to 100 parts by weight of rubber (phr), preferably 50 to 70 phr.
Typical amounts of tackifier resins comprise about 2 to 10 phr. Typical
amounts of processing aids comprise about 1 to 5 phr. Typical amounts of
antioxidant comprise 1 to 10 phr. Typical amounts of antiozonants comprise
1 to 10 phr. Typical amounts of stearic acid comprise 0.50 to about 2 phr.
Typical amounts of zinc oxide comprise 1 to 5 phr. Typical amounts of
waxes comprise 1 to 5 phr. Typical amounts of oils comprise 2 to 30 phr.
Typical amounts of peptizers 0.1 to 1 phr. The presence and relative
amounts of the above additives are not an aspect of the present invention.
The vulcanization of the composition for use as an innerliner is conducted
in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur
vulcanizing agents include elemental sulfur (free sulfur) or sulfur
donating vulcanizing agents, for example, an amine disulfide, polymeric
disulfide or sulfur olefin adducts. Preferably, the sulfur vulcanizing
agent is elemental sulfur. As known to those skilled in the art, sulfur
vulcanizing agents are used in amount ranging from about 0.2 to 8.0 phr
with a range of from about 0.5 to 5.0 being preferred.
Accelerators are used to control the time and/or temperature required for
vulcanization and to improve the properties of the vulcanizate. A single
accelerator system may be used, i.e., primary accelerator in conventional
amounts ranging from about 0.3 to 5.0 phr. In the alternative,
combinations of 2 or more accelerators may be used which may consist of a
primary accelerator which is generally used in the larger amount (0.3 to
5.0 phr), and a secondary accelerator which is generally used in smaller
amounts (0.05-1.0 phr) in order to activate and to improve the properties
of the vulcanizate. Combinations of these accelerators have been known to
produce a synergistic effect on the final properties and are somewhat
better than those produced by either accelerator alone. In addition,
delayed action accelerators may be used which are not effected by normal
processing temperatures but produce satisfactory cures at ordinary
vulcanization temperatures. Suitable types of accelerators that may be
used are amines, disulfides, guanidines, thioureas, thiazoles, thiurams,
sulfenamides, dithiocarbamate and xanthates. Preferably, the primary
accelerator is a disulfide or sulfenamide. If a secondary accelerator is
used, the secondary accelerator is preferably a guanidine, dithiocarbamate
or thiuram compound.
In practice, the various rubber compositions are used to form a laminate.
As known to those skilled in the art, the layers are produced by a press
or passing a rubber composition through a mill, calender, multihead
extruder or other suitable means. Preferably, the layers are produced by a
calender because greater uniformity is believed to be provided. The layers
are then assembled into a laminate. The uncured laminate is then
constructed as an inner surface (exposed inside surface) of an uncured
rubber tire structure, also known as the carcass. The innerliner is then
sulfur cocured with the tire carcass during the tire curing operation
under conditions of heat and pressure. Vulcanization of the tire
containing the innerliner of the present invention is generally carried
out at temperatures of between about 100.degree. C. and 200.degree. C.
Preferably, the vulcanization is conducted at temperatures ranging from
about 110.degree. C. to 180.degree. C. Any of the usual vulcanization
processes may be used such as heating in a press or mold, heating with
superheated steam or hot salt or in a salt bath. Preferably, the heating
is accomplished in a press or mold in a method known to those skilled in
the art of tire curing.
As a result of this vulcanization, the innerliner becomes an integral part
of the tire by being cocured therewith as compared to being a simple
adherent laminate. Typically, the innerliner of the present invention has
an uncured gum thickness in the range of from about 0.04-0.4 centimeters.
Preferably, the innerliner has an uncured gum thickness in the range of
from about 0.08 to about 0.02 centimeters. As a cured innerliner, the
laminate may have a thickness ranging from about 0.02 to about 0.35
centimeters. Preferably, the thickness will range from about 0.04 to about
0.15 cm thickness.
The pneumatic tire with the integral laminate innerliner may be constructed
in the form of a passenger tire, truck tire, or other type of bias or
radial pneumatic tire.
The following examples are presented in order to illustrate but not limit
the present invention.
EXAMPLE 1
A series of laminates were prepared to illustrate the various aspects of
the present invention. The nonbarrier compounds that were used included a
(1) natural rubber (NR)/styrene butadiene rubber (Plioflex.RTM. 1778)
blend in a NR/SBR weight ratio of 70/30, and (2) a styrene butadiene
rubber (Plioflex.RTM. 1502) as the sole rubber. Plioflex.RTM. 1502 is a
styrene-butadiene rubber (23% styrene) that has a Mooney viscosity of 55
and is marketed by The Goodyear Tire & Rubber Company. The NBR's used as
barrier compounds included Chemigum.RTM. RCG-4908 (NBR-43) having a 43%
acrylonitrile content, Chemigum.RTM. N-328B (NBR-39) having a 39%
acrylonitrile content, and Chemigum.RTM. N-628B (NBR-33) having a 33%
acrylonitrile content. Chemigum.RTM. NBR is commercially available from
The Goodyear Tire & Rubber Company. The mica used was a 150 mesh dry
ground phlogopite mica. The talc used was an ultra fine high purity
magnesium silicate. The carbon black used was an ASTM N-660 (GPF) black
with a dibutyl phthalate number (DPB) of 93 dm.sup.3 /kg and a nitrogen
area of 34 m.sup.2 /gm.
The NR/SBR nonbarrier compounds contained conventional amounts of carbon
black, processing oil, tackifiers, curatives, stearic acid, zinc oxide,
and accelerators. 2.25 phr of sulfur was used. These ingredients were
mixed in a Banbury mixer and sheeted out on a finishing mill.
The SBR nonbarrier compound was prepared as follows: 100 parts of SBR, 50
parts of mica, 30 parts of talc, and conventional amounts of carbon black,
zinc oxide and stearic acid were charged into a #1 Banbury mixer and mixed
for 5.5 minutes at 65 rpm. The rubber compound was discharged and sheeted
out on a finish mill. After cooling, 1.70 parts of sulfur and conventional
amounts of accelerators were added and mixed for 2 minutes. The rubber
compound was then discharged and sheeted out on a rubber mill.
Filled barrier compounds were prepared according to the procedure used for
the filled SBR nonbarrier compounds except for the various NBR's using 100
parts of NBR, 20 parts of talc, 1.7 parts of sulfur and conventional
amounts of carbon black, zinc oxide, stearic acid, and accelerators.
Unfilled SBR compounds were prepared by charging 100 parts of SBR and
conventional amounts of zinc oxide and stearic acid into a #1 Banbury
mixer and mixing together for five minutes. The rubber compound was then
discharged, sheeted out and cooled. The resulting rubber compound, along
with conventional amounts of accelerators, were mixed in a #1 Banbury
mixer by charging about half of the rubber preblend, mixing 30 seconds at
65 rpm, adding the balance of the ingredients followed by the remaining
rubber preblend and mixing for another 3.5 minutes. The rubber compound
was then discharged and sheeted out with a finish mill.
The unfilled NBR-43 gum compounds were prepared in the manner described for
the unfilled SBR compound.
Calendered layers were prepared by preheating the rubber stock on a
plastics mill and calendering it to form layers of the desired thickness
using the bottom three rolls of an inverted L four-roll calender with roll
temperatures held at 74.degree.-77.degree. C. and then rolling it up with
a polyethylene backing. Lab pressed layers were prepared using a hydraulic
press for five minutes with spacers of the desired layer thickness at
95.degree. C. and 1400 kg.
Laminates were prepared by stacking four inch square layers of the desired
thickness together with the outside layers being non-barrier layers.
The laminates were cured in a 0.089 cm thick four inch square mold for 20
minutes at 150.degree. C. The laminates were placed in the mold as
prepared.
Table I below lists the nonbarrier compound, barrier compound, type of
filler (M=mica, T=talc and CB for carbon black), the construction (number
of layers and thickness of each layer in mils with alternating layers of
nonbarrier/barrier/nonbarrier order), the oxygen permeability for the
total barrier layers used in the laminate, the oxygen permeability for the
total non-barrier layers in the laminate, the oxygen permeability of the
total laminate (barrier and non-barrier), tensile properties for each
laminate, and Gehman moduli at -35.degree. C. The Gehman test
(ASTM-1053-85) measures a torsional modulus relative to a standard wire of
known modulus at a series of temperatures. The strain involved is
relatively low, not unlike the strains experienced by a tire carcass
during normal use. The modulus of a material is a measure of stiffness.
Since -35.degree. C. is a temperature common to where tires may be used,
the stiffness of the innerliner at this temperature is important. The
lower the modulus of the sample (measured in psi), the more flexible it
will be and less likely to crack as the tire rolls. Oxygen permeabilities
were measured on a MoCon Oxytran 10/50 coulemetric instrument following
ASTM D-3985-81.
TABLE I
__________________________________________________________________________
Laminates
__________________________________________________________________________
O.sub.2 Permeability
(cc/mil/100 in.sup.2 /Day)
Non-Barrier
Non-Barrier
Barrier
Barrier
Construction
Barrier
Non Barrier
Sample
Compound
Filler Compound
Filler
(mils) Alone Alone Laminate
__________________________________________________________________________
1 (c)
NR/SBR CB NBR-43
T-CB 15/14/16 71 2992 242
2 (c)
NR/SBR CB NBR-43
T-CB 7.5/7.5/7.5/7.5/7.5
71 2992 214
3 (c)
NR/SBR CB NBR-43
T-CB 7/7/6/7/7 71 2992 547
4 (c)
NR/SBR CB NBR-39
T-CB 4/8/8/8/8/8/4
94 2992 187
5 (c)
NR/SBR CB NBR-33
T-CB 4/6/8/6/8/6/4
279 2992 586
6 (p)
SBR No NBR-43
T-CB 15/15/15 71 2098 193
7 (p)
SBR No NBR-43
No 15/15/15 106 2098 229
8 (p)
SBR No NBR-43
No 15/15/15 106 2098 283
9 (p)
SBR No NBR-43
No 15/15/15 106 2098 366
10 (p)
SBR No NBR-43
No 8/8/8/8/8 106 2098 250
11 (c)
SBR T-M-CB NBR-43
T-CB 12/7.5/12/7.5/12
71 583 183
12 (c)
SBR T-M-CB NBR-43
T-CB 16/14/17 71 583 195
13 (p)
SBR T-M-CB NBR-43
T-CB 15/15/15 71 583 179
14 (p)
SBR T-M-CB NBR-43
T-CB 15/15/15 71 583 243
15 (p)
SBR T-M-CB NBR-43
T-CB 15/15/15 71 583 124
16 (p)
SBR T-M-CB NBR-43
T-CB 8/8/8/8/8 71 583 126
17 (p)
SBR T-M-CB NBR-43
T-CB 8/8/8/8/8 71 583 112
18 (c)
SBR T-M-CB NBR-43
T-CB 7/7/7/7/7 71 583 152
19 (p)
SBR T-M-CB NBR-43
No 15/15/15 106 583 322
20 (c)
SBR T-M-CB NBR-39
T-CB 4/7/4/15/4/7/4
94 583 234
21 (c)
SBR T-M-CB NBR-39
T-CB 17/19/17 94 583 225
22 (c)
SBR T-M-CB NBR-39
T-CB 4/6/4 - 17 layers
94 583
23 (c)
SBR T-M-CB NBR-33
T-CB 4/6/4/15/4/6/4
279 583 587
24 (c)
SBR T-M-CB NBR-33
T-CB 16/16/16.5 279 583 430
25 (c)
SBR T-M-CB NBR-33
T-CB 4/6/4/6/4/6/4/6/4
279 583 362
__________________________________________________________________________
Non-Barrier
Non-Barrier
Barrier
Barrier
Construction
Tensile (psi) Gehman Moduli
Sample
Compound
Filler Compound
Filler
(mils) Break
% Elong
10%
300%
-35.degree. C.
__________________________________________________________________________
(psi)
1 (c)
NR/SBR CB NBR-43
T-CB
15/14/16 2743
434 106
1652
15660
2 (c)
NR/SBR CB NBR-43
T-CB
7.5/7.5/7.5/7.5/7.5
2802
450 110
1592
11410
3 (c)
NR/SBR CB NBR-43
T-CB
7/7/6/7/7 2552
394 90
1788
11400
4 (c)
NR/SBR CB NBR-39
T-CB
4/8/8/8/8/8/4
3212
450 126
1696
15260
5 (c)
NR/SBR CB NBR-33
T-CB
4/6/8/6/8/6/4
2013
382 96
1337
13640
6 (p)
SBR No NBR-43
T-CB
15/15/15 1057
326 101
907
7 (p)
SBR No NBR-43
No 15/15/15 616
373 67
476
8 (p)
SBR No NBR-43
No 15/15/15 670
407 64
395
9 (p)
SBR No NBR-43
No 15/15/15 640
271 66 15910
10 (p)
SBR No NBR-43
No 8/8/8/8/8 707
412 66
396
11 (c)
SBR T-M-CB NBR-43
T-CB
12/7.5/12/7.5/12
1263
408 169
810 13640
12 (c)
SBR T-M-CB NBR-43
T-CB
16/14/17 1314
419 193
840 20090
13 (p)
SBR T-M-CB NBR-43
T-CB
15/15/15 1335
387 190
902
14 (p)
SBR T-M-CB NBR-43
T-CB
15/15/15 1079
421 192
784 69840
15 (p)
SBR T-M-CB NBR-43
T-CB
15/15/15 1334
368 184
998 22080
16 (p)
SBR T-M-CB NBR-43
T-CB
8/8/8/8/8 2039
456 170
985 103100
17 (p)
SBR T-M-CB NBR-43
T-CB
8/8/8/8/8 1730
413 180
1081
66490
18 (p)
SBR T-M-CB NBR-43
T-CB
7/7/7/7/7 1592
446 174
837 118130
19 (p)
SBR T-M-CB NBR-43
No 15/15/15 964
405 170
606
20 (c)
SBR T-M-CB NBR-39
T-CB
4/7/4/15/4/7/4
2491
403 118
1575
10340
21 (c)
SBR T-M-CB NBR-39
T-CB
17/19/17 1137
351 184
915 20700
22 (c)
SBR T-M-CB NBR-39
T-CB
4/6/4 - 17 layers
1432
491 134
691
23 (c)
SBR T-M-CB NBR-33
T-CB
4/6/4/15/4/6/4
1749
353 97
1358
13640
24 (c)
SBR T-M-CB NBR-33
T-CB
16/16/16.5
879
333 159
769 24050
25 (c)
SBR T-M-CB NBR-33
T-CB
4/6/4/6/4/6/4/6/4
1529
461 135
796
__________________________________________________________________________
(c) = Calendered layers
(p) = Pressed layers
Sample 1 is an example of a laminate using a high acrylonitrile NBR for a
barrier layer sandwiched between two nonbarrier layers. A laminate would
normally be doubled for commercial use as an innerliner covered by this
invention. The non-barrier layers may be expected to provide excellent
adhesion to the tire carcass.
The Sample 12 laminate is similar to that of Sample 1 except for the change
in non-barrier material to an SBR with mica filler and talc. This
non-barrier material has an oxygen permeability of 583 cc/mil/100
in..sup.2 /Day versus 2992 measured for the non-barrier formulation used
in Sample 1. In spite of this large difference, the two laminates have
essentially the same oxygen permeability. The difference in non-barrier
material is apparent, however, in the lower ultimate tensile properties
for the laminate of Sample 12.
The laminates of Samples 21 and 24 differ from Example 12 primarily by the
acrylonitrile content of the NBR elastomer used in the barrier
formulation. The effect of acrylonitrile content on permeability is
obvious. The permeability of the laminate in Sample 12 was 195
cc/mil/100/in..sup.2 /Day. Decreasing the acrylonitrile content from 43%
to 39% for the barrier resin used in the laminate from Sample 21 results
in the permeability 225. With a barrier resin acrylonitrile content of
33%, the laminate in Sample 24 shows a sharp increase in permeability to
430.
Sample 20 presents a laminate similar in composition to the laminate from
Sample 21, but with substantially thinner barrier layers. The effect on
permeability is minimal, but the effect on the physical properties is
substantial. The Gehman moduli at -35.degree. C. for the laminate in
Sample 20 is substantially lower than observed for the laminate for Sample
21. At room temperature the ultimate tensile strength, elongation and 300%
modulus are considerably higher for the laminate in Sample 20, while the
10% modulus is higher for the laminate from Sample 21.
Sample 14 illustrates the effect of a second method of layer preparation.
As is evident from the data presented in Table I, preparing layers using a
hydraulic press in the manner described results in minimal change in
properties.
Sample 19 is similar to Sample 14 except that no filler was incorporated
into the barrier layer. This results in a substantial increase in
permeability, illustrating the importance of filler in the barrier layer
to the barrier properties of the laminate.
EXAMPLE 2
The following samples were prepared to further demonstrate the breadth of
the present invention. The nonbarrier rubbers that were used included (1)
a natural rubber (NR)/styrene-butadiene rubber (Plioflex.RTM. 1778) blend
in a NR/SBR weight ratio of 70/30 and (2) a styrene butadiene rubber
(Plioflex.RTM. 1507) as the sole rubber. Plioflex.RTM. 1507 is a styrene
butadiene rubber (23% styrene) and is marketed by The Goodyear Tire &
Rubber Company. The NBR's used as barrier materials included Chemigum.RTM.
N300 (NBR-39) having a 39% acrylonitrile content and Chemigum.RTM. N624
(NBR-33) having a 33% acrylonitrile content. The mica and talc were the
same as used in Example 1.
The NR/SBR nonbarrier compounds were processed and contained the same
ingredients and in the same amounts as used in Example 1.
The SBR nonbarrier compound was prepared as follows: 100 parts of SBR,
105.25 parts of talc and conventional amounts of zinc oxide and stearic
acid were charged into a #1 Banbury mixer and mixed for 5.5 minutes at 65
rpm. The rubber compound was discharged and sheeted out on a finish mill.
After cooling 1.1 parts of sulfur and conventional amounts of accelerators
were added and mixed for 2 minutes. The rubber compound was then
discharged and sheeted out on a rubber mill.
A talc filled NBR-39 compound was prepared according to the procedure used
for the filled SBR nonbarrier compound except 100 parts of NBR-39 and
52.47 parts of talc were used. The same amount of sulfur, zinc oxide,
stearic acid and accelerators as used.
A talc filled NBR-33 compound was prepared according to the procedure used
for the filled SBR nonbarrier compound except 100 parts of NBR-33 and 75.8
parts of talc were used. The same amount of sulfur, zinc oxide, stearic
acid and accelerators was used.
Table II below lists the nonbarrier comopund, barrier compound, type of
filler (M=mica, CB=carbon black or T=talc), the construction and the
oxygen permeability for the total laminate.
TABLE II
__________________________________________________________________________
Laminates.sup.(1)
O.sub.2 Permeability
Non-Barrier
Non-Barrier
Barrier
Barrier
Construction
Laminate
Sample
Compound
Filler Compound
Filler
(mils) cc/mil/100 sq" D
__________________________________________________________________________
26 SBR T NBR-33
T 9/8/9/8/9
352
27 SBR T NBR-33
M 10/7/10/7/10
350
28 SBR T NBR-39
T 9/7/9/7/10
250
29 NR/SBR CB NBR-33
T 7/9/8/9/8
244
30 NR/SBR CB NBR-33
M 15/15/15
353
31 NR/SBR CB NBR-39
T 15/13/15
232
__________________________________________________________________________
.sup.(1) All laminates were calendered and were constructed in the order
of nonbarrier/barrier/non-barrier layers.
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